1. Field of the Invention
The present invention relates to a new non-woven fabric material comprising hyaluronic acid derivatives, methods of production thereof, and methods of using said material in medical and pharmaceutical applications.
2. Description of Related Art
Hyaluronic acid is a natural heteropolysaccharide composed of alternating residues of D-glucuronic acid and N-acetyl-D-glucosamine. It is a linear polymer with a molecular weight of between 50,000 and 13,000,000 depending upon the source from which it is obtained, and the preparation and determination methods employed. It is present in nature in pericellular gels, in the fundamental substance of connective tissues of vertebrate organisms of which it is one of the main components, in the synovial fluid of joints, in the vitreous humor, in human umbilical cord tissues, and in cocks' combs.
There are known, specific fractions of hyaluronic acid with definite molecular weights that do not present inflammatory activity, and which can therefore be used to facilitate wound healing, to substitute for the endobulbar fluids, or which can be employed in therapy for joint pathologies by intra-articular injections, as described in European Patent No. 0 138 572 granted to Applicants on Jul. 25, 1990.
Also known are hyaluronic acid esters, wherein all or some of the carboxy groups of the acid are esterified, and their use in the pharmaceutical and cosmetic fields and in the area of biodegradable plastic materials, as described in U.S. Pat. Nos. 4,851,521 and 4,965,353 granted to Applicants.
Hyaluronic acid is known to play a fundamental role in tissue repair processes, especially in the first stages of granulation, by stabilizing the coagulation matrix and controlling its degradation, favoring the recruitment of inflammatory cells such as polymorphonuclear leukocytes and monocytes, of mesenchymal cells such as fibroblasts and endothelial cells, and in orienting the subsequent migration of epithelial cells.
It is known that the application of solutions of hyaluronic acid can accelerate healing in patients affected by bedsores, wounds and burns. The role of hyaluronic acid in the various phases that constitute tissue repair processes has been described, by the construction of a theoretical model, by Weigel P. H. et al.: "A model for the role of hyaluronic acid and fibrin in the early events during the inflammatory response and wound healing," J. Theor. Biol., 119: 219, 1986.
Studies aimed at obtaining manufactured products to apply to the skin, composed of hyaluronic acid esters as such or in mixtures with other polymers have led to the creation of various types of products. Among these are fabrics, such as gauzes of varying thickness (number of threads per centimeter), with varying dimensions, and with threads of varying denier (weight per 9000 meters of thread). Films of widely varying thickness have been proposed, as described in U.S. Pat. Nos. 4,851,521 and 4,965,353.
The use of such materials as skin coverings is limited by their stiffness, which is more or less determined according to how they were made. It is always a problem, however, when the material has to mould itself to the surface to be covered. Another drawback to the use of such materials is their poor absorbability, if any, of liquids such as solutions of disinfectants, antibiotics, antiseptics, antimicotics, proteins or wound healing substances in general, even when these are neither thick nor viscous.